As per other topics, Wayland's size, runnable hw and dependencies preclude it from being included in the base. It does not exist as an extension currently since nobody was interested in making some - if you'd like to run it, please create the extensions.

Recommended (Required to build the Wayland compositor)libinput-1.5.3, Wayland-1.12.0, wayland-protocols-1.7, and Xorg-Server-1.19.0 (with Xwayland). Additionally, Cogl-1.22.2, Clutter-1.26.0 and GTK+-3.22.4 need to be built with Wayland support.

The GNOME 3 Wayland session is really impressive, very smooth tear-free experience with much less lag than X11.

please show me how to introduce that "lag" visibly so i can reproduce this.

Easy:

Start GNOME 3 @ X (with Mutter as the hardware accelerated compositing window manager incl. Vsync). Now open a window and place the mouse cursor on the window titlebar and click and hold the left mouse button and move the mouse around to move the window around. As you can see, the mouse cursor is faster than the window movement, i.e. there's some kind of input/rendering/drawing lag.

This will also be true and in many cases even worse than GNOME 3 with other X shells using compositing window managers. Take XFCE4 + Compton for example. Running XFCE4 with Compton results in proper VSync (unlike xfwm4). However, there's some huge input lag. In this case, the window movement is even much slower than the mouse cursor (compared to GNOME 3 @ X). So XFCE4 + Compton is an even better example.

In comparison:

Start GNOME 3 @ Wayland and do the same (i.e. move a window around). You will see that the mouse cursor and window movement is in perfect sync and it feels much less laggy and rock solid.

The same is also true for running Wayland @ Weston.

With Wayland there's no tearing and not such a lag as mentioned above. With Wayland it feels as good as with Windows Vista/7/8/8.1/10 @ DWM.

If you want to try out the GNOME 3 @ Wayland session, you can boot up the latest Fedora Rawhide live session:

it's a usual tactic i observe in open source projects: tell all slightly-related projects that the other competing projects are better. they don't look at why or care about any technicalities. they just think they do it for the greater good, that people will get back to work and then make more useful software (i.e. support their crappy feature request), cause all that was needed for greatness is their friendly encouragement.

I am not going to do the work of making a Wayland iso. As you're the one interested in it, the onus is on you to do so. Without a comparable ISO there can't be byte-exact numbers.

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Wayland and Weston can be run with software rendering since v1.1:

Yes. It still requires KMS, and more importantly, the *client* apps still require GL, ie mesa. There may be clients that can fall back to software rendering, but the majority will only support GL on Wayland.

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Which dependencies?

KMS, libinput, mesa, others. I doubt you can get the lag-free experience using software rendering only.